fix minor bug

app.py

@@ -233,7 +233,7 @@ def detect_vid(vid,model):
     current_video_name = "current_vid.mp4"  
     vid_folder = "Inference/videos"
     try:
-        mkdir(vid_folder)
+        os.mkdir(vid_folder)
     except FileExistsError:
         print(f"Folder already exists.")
     save_current_path = os.path.join("./Inference/videos", current_video_name)